1. Field of the Invention
The invention relates to an assembly package and, more particularly, to an assembly package that integrates more than one die into one package by using at least one signal transmission plate.
2. Description of the Related Art
During the recent years, due to the steady increase of demand of consumer electronic products, namely, cellular phones, personal digital assistants (PDAs) and digital cameras, package structures are developed toward being light in weight and small in size with short signal transmission distances. Based upon such trend, in order to save package area as well as to improve problems such as signal distortion, delay or power loss, an assembly package integrates at least one die into a same package structure by perpendicular stacking.
Referring to FIG. 1, a conventional ball grid array (BGA) package 1 mainly includes a bottom die 12, a top die 15, and a plurality of conductive wires 16 and 17. The bottom die 12 is provided on the substrate 11 and the top die 15 is provided on the bottom die 12. Between the top die 15 and the bottom die 12, a non-conductive adhesive 13, silver paste for example, is applied, so that the top die 15 is fixed to the bottom die 12 while also insulated from the bottom die 12. The bottom die 12 and the top die 15 are signally connected with the substrate 11 via the conductive wires 16 and 17, gold wires for example, respectively. Thermosetting plastics are used as the molding compound 18, through molds and by a molding press, to fill and encapsulate the conductive wires 16 and 17, the bottom die 12, and the top die 15, thereby casting by baking. In addition, on the other side of the substrate 11 is provided with solder balls 19, which are placed onto the solder pads on the substrate 11 and connected with the exterior to transmit signals.
With such an assembly package technique, two or more dies may be integrated into a same package. Nevertheless, by using conductive wires to electrically connect I/O pins of individual die with the substrate for signal transmission, the signal transmission quality of the die may be affected by the transmission distance and the number of conductive wires. More particularly, driven by the multi-function and high performance requirements demanded by the modern electronic products, dies having high 110 pin-counts are the development trend. However, the longer the transmission distance of conductive wires gets, the noise increases accordingly, and the signal distortion and hysteresis become more apparent, thereby dropping the signal transmission quality.
Therefore, it is a vital task to improve the signal transmission quality and speed up the signal transmission rate of assembly packages.
In view of the above issue, the object of the invention is to provide an assembly package having good signal transmission quality and fast transmission rate.
To achieve the above object, the invention provides an assembly package including a substrate, a first die, at least one signal transmission plate, at least one second die, a plurality of conductive wires, and a molding compound. The first die is electrically connected to the substrate using flip-chip bonding. The signal transmission plate is provided on the first die and has at least one insulating layer, at least one layout wire layer, and a solder mask layer. The layout wire layer is formed on the insulating layer, and the solder mask layer is formed on the layout wire layer. The solder mask layer exposes partial area of the layout wire layer at the center and peripheries of the signal transmission plate to form a plurality of die bonding pads and a plurality of wire bonding pads. The second die is electrically connected with the die bonding pads using flip-chip bonding, and the wire bonding pads are electrically connected to the substrate via the conductive wires so that signals from the second die are transmitted to the substrate. Furthermore, thermosetting plastics are used to encapsulate the first die, the signal transmission plate, the second die and the conductive wires.
The assembly package of the invention employs flip-chip bonding, so that the signals from the first die (the bottom die) are transmitted to the substrate. Therefore, imperfect electricity caused by using lead connection is prevented. Also, the second die also utilizes flip-chip bonding so that the signals are transmitted to the signal transmission plate and then to the substrate via the conductive wires. As a result, the conductive wires are not required to connect to the joints on the top die; only the signal transmission plate is needed to connect with the wire bonding pads, and signals from the top die can be transmitted to the substrate. In other words, the signal transmission quality is improved, and the signal transmission rate is also increased, for that the transmission distance of the conductive wires is shortened.